Semiconductor device

ABSTRACT

A semiconductor device includes a first semiconductor chip which includes a first power supply terminal and into which a circuit block which is operated by a power supply voltage supplied to the first power supply terminal is integrated, a power circuit that includes switching transistors and supplies the power supply voltage to the first power supply terminal, and a DCDC control unit that is formed on the first semiconductor chip and generates a control signal for controlling the turning on and off of the switching transistors in response to an information signal from the circuit block and a voltage information signal corresponding to an output voltage from the power circuit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2013-32110, filed on Feb. 21, 2013; theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to semiconductor devicesincluding a power circuit and a semiconductor chip which is driven by anoutput voltage from the power circuit.

BACKGROUND

A method has been known in which an integrated circuit called an SoC(System on Chip) is designed by integrating a series of necessaryfunctional system into one semiconductor chip. Since various functionsare integrated into one semiconductor chip, a high-performancesemiconductor device is provided. However, a load current is changed bythe functions performed on the semiconductor chip, which results in avariation in power supply voltage. In recent years, a technique has beenproposed which selectively supplies a plurality of power supply voltagesgenerated by a DCDC converter according to the operation state of eachfunctional block in a semiconductor device including a semiconductorchip into which various functional blocks are integrated.

When the power supply voltage varies, the operation speed of the circuitof the functional block on the semiconductor chip also varies. As thepower supply voltage increases, the operation speed of the circuitincreases. As the power supply voltage is reduced, the operation speedof the circuit is reduced. When the power supply voltage is reduced tobelow a predetermined threshold voltage, the operation of the circuit ofthe functional block is likely to be disabled. In addition, when themanufacturing conditions of each semiconductor chip vary, the operationspeed of the circuit of the functional block formed in the semiconductorchip varies. In some cases, EMI (Electro Magnetic Interference) occursdue to noise from a power circuit, depending on the relationship betweenthe switching frequency of the power circuit which supplies the powersupply voltage and the operating frequency of the functional block onthe semiconductor chip. Therefore, there is a demand for a power supplysystem capable of supplying an appropriate power supply voltage to asemiconductor chip according to various environments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a semiconductor device according to afirst embodiment;

FIG. 2 is a diagram illustrating a DCDC control unit according to asecond embodiment;

FIG. 3 is a diagram illustrating a DCDC control unit according to athird embodiment;

FIG. 4 is a diagram illustrating the operation of the DCDC control unitaccording to the third embodiment;

FIG. 5 is a diagram illustrating a semiconductor device according to afourth embodiment;

FIG. 6 is a diagram illustrating an example of a DCDC control unit usedin the semiconductor device according to the fourth embodiment;

FIG. 7 is a diagram illustrating the operation of a DCDC control unitaccording to a fifth embodiment;

FIG. 8 is a diagram illustrating the operation of a DCDC control unitaccording to a sixth embodiment;

FIG. 9 is a diagram illustrating a DCDC control unit according to aseventh embodiment;

FIG. 10 is a diagram illustrating the structure of a semiconductordevice according to an eighth embodiment;

FIG. 11 is a diagram illustrating the structure of a semiconductordevice according to a ninth embodiment;

FIG. 12 is a diagram illustrating the structure of a semiconductordevice according to a tenth embodiment;

FIG. 13 is a diagram illustrating the structure of a semiconductordevice according to an eleventh embodiment;

FIG. 14 is a diagram illustrating the structure of a semiconductordevice according to a twelfth embodiment;

FIGS. 15A and 15B are diagrams illustrating examples of a serializer anda deserializer which can be used in the embodiment illustrated in FIG.14; and

FIGS. 16A to 16N are diagrams illustrating the relationship betweensignals supplied to a serializer and a deserializer in the embodimentillustrated in FIG. 14 and signals output therefrom.

DETAILED DESCRIPTION

In general, according to one embodiment, a semiconductor device includesa first semiconductor chip which includes a first power supply terminaland into which a circuit block that is operated by a power supplyvoltage supplied to the first power supply terminal is integrated, apower circuit that includes a switching transistor and supplies thepower supply voltage to the first power supply terminal, and a controlcircuit that is formed on the first semiconductor chip and generates acontrol signal for controlling the turning on and off of the switchingtransistor in response to an information signal from the circuit blockand a voltage information signal corresponding to an output voltage fromthe power circuit.

Exemplary embodiments of semiconductor device will be explained below indetail with reference to the accompanying drawings. The presentinvention is not limited to the following embodiments.

FIG. 1 is a diagram illustrating the structure of a semiconductor deviceaccording to a first embodiment. A logic circuit 4 with a predeterminedfunction is formed in a semiconductor chip 1. The logic circuit 4includes a sensor 5. The sensor 5 detects various kinds of informationabout the logic circuit 4. For example, the sensor 5 detectsinformation, such as an operating voltage, an operating current, and thetemperature. The information of the sensor 5 is supplied to a DCDCcontrol unit 6. The semiconductor chip 1 includes a plurality ofelectrode pads. A power circuit applies an output voltage Vout as apower supply voltage VDD for the semiconductor chip 1 to an electrodepad 2. A signal corresponding to the power supply voltage VDD issupplied to the DCDC control unit 6. The DCDC control unit 6 supplies,to an electrode pad 3, a pulse width control signal (hereinafter,referred to as a PWM signal) for controlling the operation of the powercircuit such that the power supply voltage VDD becomes a desiredvoltage, in response to the signal from the sensor 5 and the signalcorresponding to the power supply voltage VDD.

The power circuit includes a driver 7 which responds to the PWM signalsupplied to the electrode pad 3. The driver 7 controls the ratio (Duty)of the turning on and off of a first PMOS switching transistor 8 and asecond NMOS switching transistor 9 in response to the PWM signal. Thedriver 7 includes, for example, a plurality of stages of CMOS inverters(not illustrated). When the first PMOS switching transistor 8 is turnedon, the second NMOS switching transistor 9 is turned off. Then, acurrent is supplied from the DC power supply 10 to a capacitor 12through the first PMOS switching transistor 8 and an inductor 11 and anoutput voltage Vout increases. On the other hand, when the first PMOSswitching transistor 8 is turned off, the second NMOS switchingtransistor 9 is turned on. Then, charge stored in the capacitor 12 isdischarged through the second NMOS switching transistor 9 and the outputvoltage Vout is reduced. The duty of the turning on and off of the firstPMOS switching transistor 8 and the second NMOS switching transistor 9can be adjusted to obtain a desired output voltage Vout.

According to this embodiment, signals indicating various kinds ofinformation are directly supplied from the sensor 5 of the logic circuit4 to the DCDC control unit 6 which is formed in the semiconductor chip 1having the logic circuit 4 formed therein. Therefore, it is possible tocontrol the output voltage Vout from the power circuit on the basis ofvarious kinds of information from the sensor 5, without any delay, andresponse to the operation state of the logic circuit 4 is improved. Inaddition, since the DCDC control unit 6 is formed in the semiconductorchip 1, it is possible to supply various kinds of information to theDCDC control unit 6 using lines (not illustrated) formed in thesemiconductor chip 1, without increasing the number of electrode pads inthe semiconductor chip 1.

FIG. 2 is a conceptual diagram illustrating a DCDC control unitaccording to a second embodiment. A DCDC control unit 15 according tothis embodiment includes a plurality of circuit structures correspondingto a plurality of control modes. For example, when mode 1 is selected, astructure 22 of the DCDC control unit 15 having an error calculationcircuit 26 and a compensation circuit 27 as components is selected. Themode is selected by multiplexers 20 and 21 which respond to selectionsignals from a mode selection circuit 28. Modes 1 to N are appropriatelyselected depending on information (Data) supplied from the logic circuit4. Different circuit structures 22 to 25 of the DCDC control unit 15 areselected depending on each mode. Signals which are processed bydifferent circuit structures are supplied to a PWM generation circuit 29through the multiplexer 21. The PWM generation circuit 29 outputs a PWMsignal for controlling the duty of the turning on and off of a switchingtransistor (not illustrated) of a power circuit.

FIG. 3 is a diagram illustrating a DCDC control unit and a power circuitaccording to a third embodiment. In the third embodiment, the samecomponents as those in the first and second embodiments are denoted bythe same reference numerals and the description thereof will not berepeated. This embodiment relates to a structure for avoiding the powernoise interference of a semiconductor device. For example, a circuitstructure 23 when mode 2 is selected in the embodiment illustrated inFIG. 2 is configured. In this embodiment, the circuit structure 23 ofthe DCDC control unit includes an error calculation circuit 30 thatcompares a power supply voltage VDD with a predetermined referencevoltage Vref and outputs an error signal on the basis of the comparisonresult. The output from the error calculation circuit 30 is supplied toa compensation circuit 31. The compensation circuit 31 can perform, forexample, PID (Proportional Integral Derivative) control such that theerror between the power supply voltage VDD and the reference voltageVref is close to zero (0). The output from the compensation circuit 31is supplied to a digital delay conversion circuit 32. The digital delayconversion circuit 32 converts the output signal from the compensationcircuit 31 into a digital value associated with the amount of delay. Theoutput from the digital delay conversion circuit 32 is supplied to areset signal input terminal R of an RS latch circuit 33. The resetsignal of the RS latch circuit 33 controls the falling of a PWM signal.

An SoC clock signal indicating the operating frequency and phase of apredetermined logic circuit (not illustrated) formed in thesemiconductor chip is supplied to one input terminal of afrequency/phase adjustment circuit 34. The PWM signal, which is theoutput from the RS latch circuit 33, is supplied to the other inputterminal of the frequency/phase adjustment circuit 34. Thefrequency/phase adjustment circuit 34 compares the frequencies andphases of the SoC clock signal and the PWM signal. The frequency/phaseadjustment circuit 34 supplies a control signal whose rising time hasbeen changed depending on the comparison result between the SoC clocksignal and the PWM signal to a set input terminal of the RS latchcircuit 33 and adjusts the frequencies and phases such that thefrequency and phase of the SoC clock signal are different from those ofthe PWM signal. The rising of the PWM signal, which is the output signalfrom the RS latch circuit 33, is controlled by the signal supplied tothe set signal input terminal S to control the frequency and phase ofthe PWM signal. The falling of the PWM signal is controlled by theoutput from the digital delay conversion circuit 32 and the duty of theturning on and off of the switching transistor of the power circuit iscontrolled.

The PWM signal whose rising and falling have been controlled is suppliedfrom the RS latch circuit 33 to a driver 7. The turning on and off ofthe first PMOS switching transistor 8 and the second NMOS switchingtransistor 9 are controlled by the output from the driver 7 to which thePWM signal is supplied. The rising of the PWM signal is controlled tocontrol the switching frequency of the power circuit to the frequencyand phase different from those of the SoC clock signal. Therefore, it ispossible to avoid EMI due to power supply noise which is generated whenthe frequency and phase of the SoC clock signal, which are the operatingfrequency of the logic circuit (not illustrated) operating in thesemiconductor chip, are equal to the switching frequency and phase ofthe power circuit.

FIG. 4 is a diagram illustrating the control flow of the circuitstructure 23 of the DCDC control unit illustrated in FIG. 3. Thefrequency and phase of the SoC clock signal, which are the operatingfrequency of a predetermined logic circuit (not illustrated) formed inthe semiconductor chip, are monitored (S101). The frequency and phaseare compared with the PWM signal for controlling the frequency and phaseof the power circuit and it is determined whether the frequency andphase deviate from the frequency and phase of the power circuit (S102).When they deviate from each other, the monitoring operation iscontinuously performed. When they are identical to each other, controlis performed such that they deviate from each other (S103). When thefrequency and phase of the power circuit deviate from the operatingfrequency and phase of the SoC clock signal, it is possible to avoid EMIdue to power supply noise. However, a multiplier circuit (notillustrated) which multiplies the frequency of the PWM signal may beprovided in the frequency/phase adjustment circuit 34 and control may beperformed such that the harmonic signal component of the PWM signal isnot identical to the operating frequency and phase of the SoC clocksignal.

FIG. 5 is a diagram illustrating a semiconductor device according to afourth embodiment. In the fourth embodiment, the same components asthose in the first to third embodiments are denoted by the samereference numerals and the description thereof will not be repeated.This embodiment relates to a structure for preventing a rush currentwhen a power supply voltage rises. A plurality of power domains 51 to 53is formed in a semiconductor chip 1. Circuit block regions in which onepower supply voltage is applied and which perform predeterminedfunctions are represented by the power domains 51 to 53. The powerdomains 51 to 53 form, for example, a CPU (Central Processing Unit), aDSP (Digital Signal Processor), or a predetermined logic circuit. Thepower domains 51 to 53 include current sensors 501 to 503 which detectthe operating currents of the power domains 51 to 53, respectively. Eachof the current sensors 501 to 503 can be configured such that it detectsthe voltage generated between both ends of a resistor connected to, forexample, a power line (not illustrated) using a differential amplifiercircuit (not illustrated), or it can be formed by a current mirrorcircuit (not illustrated). The sensing signals Isense1 to Isense3 fromthe current sensors 501 to 503 are supplied to a DCDC control unit 24.The sensing signal Isense4 from a current sensor 55 which detects thecurrent of the power supply voltage VDD is also supplied to the DCDCcontrol unit 24.

FIG. 6 is a diagram illustrating an example of the circuit structure ofthe DCDC control unit 24 which is used in the semiconductor deviceaccording to the fourth embodiment illustrated in FIG. 5. For example,the DCDC control unit 24 according to this embodiment is configured asthe circuit structure 24 when mode 3 is selected in the embodimentillustrated in FIG. 2. The DCDC control unit 24 according to thisembodiment includes a Slope control signal generation circuit 60 thatgenerates a ramp signal with a predetermined slope according topredetermined current setting signals Preset1 to PresetN which are setso as to correspond to each power domain. Current control output signalsIctrl1 to IctrlN with predetermined slopes are output from the Slopecontrol signal generation circuit 60 and are then supplied to comparisoncircuits 61 to 62. The comparison circuits 61 to 62 compare the currentcontrol output signals Ictrl1 to IctrlN with the sensing signals Isense1to IsenseN from the current sensors 501 to 503 in the power domains 51to 53 which are formed in the semiconductor chip 1.

When the comparison results of the comparison circuits 61 to 62 showthat, when the sensing signals Isense1 to IsenseN detected from thepower domains are more than the current control output signals Ictrl1 toIctrlN, reset signals Reset1 to ResetN are output from the comparisoncircuits 61 to 62 and are then supplied to an OR circuit 63. The outputfrom the OR circuit 63 is supplied to a mode selection circuit 64. TheDCDC control unit 24 according to this embodiment includes an errorcalculation circuit 65 that compares the power supply voltage VDD with apredetermined reference voltage Vref and calculates the errortherebetween. The output from the error calculation circuit 65 issupplied to a compensation circuit 66 which performs PID control. Thecompensation circuit 66 performs the PID control such that the errorbetween the power supply voltage VDD and the reference voltage Vref isclose to zero (0). The output from the compensation circuit 66 issupplied to a digital delay conversion circuit 67. The digital delayconversion circuit 67 converts the output signal from the compensationcircuit 66 to a digital value associated with the amount of delay. Theoutput from the digital delay conversion circuit 67 is supplied to themode selection circuit 64.

When the mode selection circuit 64 selects the start mode, control basedon the current control output signals Ictrl1 to IctrlN whose slopes areset on the basis of predetermined current setting signals Preset1 toPresetN is selected and the output signal from the OR circuit 63 issupplied to a reset input terminal R of an RS latch circuit 68. When thenormal mode is selected, a signal based on control which makes the powersupply voltage VDD equal to the predetermined reference voltage Vref issupplied from the mode selection circuit 64 to the reset input terminalR of the RS latch circuit 68. The PWM signal whose rising is controlledby a clock signal (clock) supplied to a set input terminal S of the RSlatch circuit 68 and whose falling is controlled by the clock signalfrom the mode selection circuit 64 is output from the RS latch circuit68.

According to this embodiment, the current when the power supply voltagerises in each power domain can be controlled to a predetermined slope.Therefore, it is possible to suppress a rush current when the powersupply voltage rises.

FIG. 7 is a diagram illustrating the operation of a DCDC control unitaccording to a fifth embodiment. In this embodiment, each power domain(not illustrated) formed in a semiconductor chip includes a sensor (notillustrated) which detects a change in the operation mode of each powerdomain. Each sensor detects information about a change in the operationmode of each power domain and supplies the information to the DCDCcontrol unit (not illustrated). The information about the change in theoperation mode is, for example, information indicating a change in anapplication executed by each power domain and indicates informationabout a change from an image processing application to a simple logicaloperation mode. Since the load current of the power domain is changeddepending on a change in the operation mode, the operating voltage ofeach power domain is changed. The information about the change in theoperation mode is supplied to the DCDC control unit and feedforwardcontrol is performed to improve a load response speed. For example, amode selection signal (not illustrated) which is supplied to each powerdomain in order to change the operation mode may be detected as theinformation about the change in the operation mode.

A control step is performed as follows. First, the information about thechange in the operation mode, such as information indicating a change inthe application executed by each power domain, is monitored (S701).Then, it is detected whether a change (event) in the operation modeoccurs (S702). When the change in the operation mode does not occur, themonitoring operation is continuously performed. When the change in theoperation mode occurs, it is determined that the operation mode ischanged to a mode in which the load current increases (S703). When theoperation mode is changed to the mode in which the load currentincreases, the duty of the turning on and off of a switching transistor(not illustrated) in a power circuit is adjusted and control isperformed to increase an output voltage (S704). On the other hand, whenthe operation mode is changed to a mode in which the load current isreduced, the duty of the turning on and off of the switching transistor(not illustrated) in the power circuit is adjusted and control isperformed to reduce the output voltage (S705). The feedforward controlmakes it possible to improve a load response. For example, a delaysignal corresponding to each mode change is prepared in advance, theamount of delay of a digital delay conversion circuit (corresponding to,for example, reference numeral 67 in FIG. 6) is controlled on the basisof the occurrence of a mode change event, and the duty of the turning onand off of the switching transistor (not illustrated) of the powercircuit is controlled to adjust the output voltage from the powercircuit.

FIG. 8 is a diagram illustrating the operation of a DCDC control unitaccording to a sixth embodiment. In this embodiment, each power domain(not illustrated) formed in a semiconductor chip includes a sensor (notillustrated) which senses information about the turning on and off ofthe power supply voltage of each power domain. That is, informationindicating whether each power domain operates is directly supplied tothe DCDC control unit (not illustrated) formed in a semiconductor chip.As the number of power domains which operate increases, a load currentincreases. It is possible to improve a load response by supplying theinformation about the turning on and off of the power domain to the DCDCcontrol unit and performing feedforward control. For example, an enablesignal (not illustrated) which is supplied in order to control theturning on and off of the power domain may be detected as theinformation indicating whether each power domain operates.

A control step is performed as follows. First, information about theswitching between the turning on and off of the power supply voltage ofeach power domain is monitored (S801). Then, it is detected whether theswitching (event) between the turning on and off of the power supplyvoltage of each power domain occurs (S802). When the switching betweenthe turning on and off of the power supply voltage of each power domaindoes not occur, the monitoring operation is continuously performed. Whenthe switching between the turning on and off of the power supply voltageof each power domain occurs, it is determined whether a load current isincreased by the switching (S803). As the number of power domains inwhich the power supply voltage is turned on increases, the load currentincreases. As the number of power domains in which the power supplyvoltage is turned off increases, the load current is reduced. When theload current is increased, control is performed such that the duty ofthe turning on and off of a switching transistor (not illustrated) in apower circuit is adjusted to increase the output voltage (S804). On theother hand, when the load current is reduced, control is performed suchthat the duty of the turning on and off of the switching transistor (notillustrated) in the power circuit is adjusted to reduce the outputvoltage (S805). The feedforward control makes it possible to improve aload response. For example, a delay signal corresponding to the turningon and off of each power domain is prepared in advance, the amount ofdelay of a digital delay conversion circuit (corresponding to, forexample, reference numeral 67 in FIG. 6) is controlled on the basis ofthe occurrence of the switching between the turning on and off of thepower supply voltage, and the duty of the turning on and off of theswitching transistor (not illustrated) in the power circuit iscontrolled to adjust the output voltage from the power circuit.

FIG. 9 is a diagram illustrating a DCDC control unit according to aseventh embodiment. For example, a DCDC control unit 25 according tothis embodiment is configured as the circuit structure 25 when mode N isselected in the embodiment illustrated in FIG. 2. The DCDC control unit25 according to this embodiment includes an error calculation circuit 90which compares a predetermined reference voltage Ref voltage with asense voltage indicating a power supply voltage VDD and calculates errorsignal error value 1 corresponding to the difference between thesevoltages. A second error calculation circuit 91 compares a predeterminedreference temperature signal Ref temperature with a sense temperatureindicating the temperature of a power domain (not illustrated) andcalculates error signal error value 2 corresponding to the differencebetween these temperatures. Since the operation speed of the powerdomain formed in a semiconductor chip is changed depending on thetemperature, temperature information is an index indicating theoperation state of each power domain formed in the semiconductor chip.For example, since a band gap voltage is changed in proportion to thetemperature, it is possible to detect the temperature information bydetecting the band gap voltage of the power domain formed in thesemiconductor chip.

A third error calculation circuit 92 compares a predetermined referencedelay signal Ref delay with a sense delay indicating the delay of theoperation speed of the power domain and calculates error signal errorvalue 3 corresponding to the difference between these delays. Forexample, a plurality of inverters is formed in the power domain and thenumber of inverters which respond within a predetermined period of timeis counted to detect the amount of delay of the operation speed of thepower domain. Error signal error values 1 to 3 of the error calculationcircuits 90 to 92 are supplied to an adder circuit 93 and are thenadded. The output from the adder circuit 93 is supplied to acompensation circuit 94 and PID control is performed. A PWM signal forcontrolling the duty of the turning on and off of a switching transistor(not illustrated) in a power circuit (not illustrated) such that the sumof the error signals is zero (0) on the basis of the output signal fromthe adder circuit 94 is output from a PWM generation circuit 95 by thePID control.

As the temperature increases, the operation speed of the power domainincreases. In addition, as the power supply voltage VDD increases, theoperation speed of the power domain increases. Therefore, thetemperature and operation speed of the power domain can be associatedwith the power supply voltage VDD. Information about the temperature ofthe power domain formed in the semiconductor chip and information aboutthe operation speed of the power domain are detected. Then, theinformation items are directly supplied to the DCDC control circuitformed on the semiconductor chip in which the power domains are formedand the power supply voltage VDD is controlled on the basis of theinformation items. In this way, it is possible to rapidly control thepower supply voltage VDD according to a variation in the operationcharacteristics of the power domain which occurs in each semiconductorchip.

FIG. 10 is a diagram illustrating the structure of a semiconductordevice according to an eighth embodiment. The same components as thosein the first to seventh embodiments are denoted by the same referencenumerals and the description thereof will not be repeated. In thisembodiment, the operating voltage of each power domain formed in asemiconductor chip 1 is monitored, the power domain in which a reductionin the operating voltage is the maximum is specified, and control isperformed to increase a power supply voltage VDD such that the margin ofthe operating voltage can be ensured. In this way, the process isperformed in order to avoid the generation of a disabled power domaindue to a low power supply voltage VDD. The operating voltage means thepower supply voltage of each power domain and is used for distinctionfrom the voltage which is supplied from a power circuit to thesemiconductor chip 1 for convenience of explanation, which holds for thefollowing embodiments.

In this embodiment, power domains 100 to 102 include sensors 140 to 142,respectively. A signal from each sensor is supplied to an errorcalculation circuit 104 of a DCDC control unit 103 formed in thesemiconductor chip 1. In addition, an AD converter 107 convertsinformation about the power supply voltage VDD into a digital value andthe digital value is supplied to the error calculation circuit 104. Forexample, the power domain 100 operates at an operating voltage of 1.2 V.Similarly, it is assumed that the power domain 101 operates at 1.09 Vand the power domain 102 operates at 1.25 V.

When the operating voltage is reduced, delay in the operation of thepower domain increases. When the operating voltage is equal to or lessthan a predetermined threshold value, it is difficult for the powerdomain to operate. Therefore, in this embodiment, when there is a powerdomain which operates at an operating voltage close to the thresholdvalue, control is performed such that an output voltage Vout from thepower circuit is increased to increase the power supply voltage VDD,thereby preventing the operation of the power domain in thesemiconductor chip 1 from being disabled. For example, when thethreshold value of the operating voltage is 1.05 V, it is detected thatthe operating voltage of the power domain 101, that is, 1.09 V is closeto the threshold value and an operation of increasing the power supplyvoltage VDD from 1.2 V to 1.22 V is performed. Control is performed suchthat a reference voltage Vref supplied to the error calculation circuit104 of the DCDC control unit 103 is increased to 1.22 V to increase theoutput voltage Vout from the power circuit, thereby increasing the powersupply voltage VDD to 1.22 V. The output signal from the errorcalculation circuit 104 is supplied to a compensation circuit 105. Thecompensation circuit 105 performs PID control and the PWM generationcircuit 106 supplies a PWM signal for increasing the ratio of theturning-on of a switching transistor 8 in the power circuit to increasethe output voltage Vout from the power circuit to a driver 7.

According to this embodiment, the output voltage Vout from the powercircuit is controlled such that the operating voltage of each powerdomain is not equal to or less than a predetermined threshold value.Therefore, it is possible to prevent the operation of the power domainin the semiconductor chip 1 from being disabled due to a reduction inthe power supply voltage VDD.

FIG. 11 is a diagram illustrating the structure of a semiconductordevice according to a ninth embodiment. The same components as those inthe first to eighth embodiments are denoted by the same referencenumerals and the description thereof will not be repeated. Thisembodiment relates to a structure which reduces a power supply voltageVDD to the minimum value to reduce power consumption. Sensors 143 to 145which are respectively provided in power domains 110 to 112 directlysupply information about the operating voltage of each power domain toan error calculation circuit 114 of a DCDC control unit 113 which isformed in a semiconductor chip 1 having the power domains 110 to 112formed therein. A signal, which is a digital value converted by an ADconverter 117, is supplied to the error calculation circuit 114.

When the operating voltage of each power domain in the semiconductorchip 1 has a sufficient margin with respect to a predetermined thresholdvoltage, control is performed to reduce the power supply voltage VDD.For example, it is assumed that, when the threshold value of theoperating voltage of each of the power domains 110 to 112 formed in thesemiconductor chip 1 is 1.09 V, the power domain 111 has the lowestoperating voltage of 1.15 V in the voltage information obtained from thepower domains 110 to 112 in the semiconductor chip 1. In this case, theoperating voltage of each of the power domains 110 to 112 formed in thesemiconductor chip 1 has a sufficient margin and control is performed toreduce the power supply voltage VDD from, for example, 1.2 V to 1.15 V.It is possible to perform control such that the power supply voltage VDDis reduced to 1.15 V by setting the reference voltage Vref supplied tothe error calculation circuit 114 of the DCDC control unit 113 to 1.15V. The output signal from the error calculation circuit 114 is suppliedto a compensation circuit 115. The compensation circuit 115 performs PIDcontrol and a PWM generation circuit 116 supplies a PWM signal fordecreasing the ratio of the turning-on of a switching transistor 8 in apower circuit to reduce the output voltage Vout from the power circuitto a driver 7.

According to this embodiment, information indicating the state of theoperating voltage of each power domain is directly supplied to the DCDCcontrol unit which is formed in the semiconductor chip 1 having thepower domains formed therein. Therefore, when there is a margin in theoperating voltage of each power domain, control can be performed suchthat the power supply voltage VDD is rapidly decreased to reduce powerconsumption.

FIG. 12 is a diagram illustrating the structure of a semiconductordevice according to a tenth embodiment. The same components as those inthe first to ninth embodiments are denoted by the same referencenumerals and the description thereof will not be repeated. Thisembodiment relates to a so-called multi-channel structure in whichdifferent power supply voltages are supplied to each power domain formedin a semiconductor chip 1. In this embodiment, the semiconductor chip 1includes two power domains 120 and 121. A voltage of 1.0 V is suppliedas a power supply voltage VDD1 to the power domain 120 through anelectrode pad 162. A voltage of 3.3 V is supplied as a power supplyvoltage VDD2 the power domain 121 through an electrode pad 163. Thepower domains 120 and 121 include sensors 146 and 148, respectively, andthe outputs from the sensors 146 and 148 are supplied to DCDC controlunits 147 and 149. An AD converter 164 converts information about thepower supply voltage VDD1 into a digital value and the digital value issupplied to the DCDC control unit 147 of the power domain 120. An ADconverter 165 converts information about the power supply voltage VDD2into a digital value and the digital value is supplied to the DCDCcontrol unit 149 of the power domain 121.

The DCDC control units 147 and 149 perform control corresponding to theabove-mentioned various control modes. The outputs from the DCDC controlunits 147 and 149 are supplied to a serializer 150 and are thenconverted into parallel signals by a deserializer 151 which is providedoutside the semiconductor chip 1. Then, the parallel signals aresupplied to drivers 152 and 157. The serial-parallel conversion by theserializer 150 and the deserializer 151 makes it possible to output twoPWM signals PWM1 and PWM2 from one electrode pad 2 of the semiconductorchip 1 to the drivers 152 and 157, respectively. The serializer 150 maybe, for example, an EOR circuit (not illustrated). The deserializer 151may be a two-stage T-type flip-flop circuit in which a signal isdirectly supplied to one stage and an inverted signal is supplied to theother stage.

The first driver 152 controls an output voltage Vout1 from a first powercircuit including a PMOS switching transistor 153, an NMOS switchingtransistor 154, an inductor 155, and a capacitor 156. The second driver157 controls an output voltage Vout2 from a second power circuitincluding a PMOS switching transistor 158, an NMOS switching transistor159, an inductor 160, and a capacitor 161. The first output voltageVout1 and the second output voltage Vout2 are supplied to the electrodepads 162 and 163 of the semiconductor chip 1, respectively. Thecontrolled power supply voltages VDD1 and VDD2 are supplied to the twopower domains 120 and 121 through the electrode pads 162 and 163,respectively.

According to this embodiment, the power supply voltages VDD1 and VDD2 ofthe semiconductor device with a multi-channel structure can becontrolled in various control modes and then supplied to the powerdomains 120 and 121, respectively. The DCDC control units 147 and 149formed in the semiconductor chip 1 in which the power domains 120 and121 are formed can rapidly control the power supply voltages VDD1 andVDD2 corresponding to the characteristics or operation state of thepower domains 120 and 121 and supply the controlled power supplyvoltages VDD1 and VDD2 to the power domains 120 and 121, respectively.The use of the serializer 150 and the deserializer 151 makes it possibleto output two PWM signals PWM1 and PWM2 for controlling the drivers 152and 157 of two power circuits from the common electrode pad 2 of thesemiconductor chip 1. Therefore, it is possible to prevent an increasein the number of electrode pads. However, the outputs from the DCDCcontrol units 147 and 149 may be directly supplied from two electrodepads to the drivers 152 and 157, respectively.

FIG. 13 is a diagram illustrating the structure of a semiconductordevice according to an eleventh embodiment. The same components as thosein the first to tenth embodiments are denoted by the same referencenumerals and the description thereof will not be repeated. Thisembodiment relates to a multi-phase power supply structure. That is, thesemiconductor device includes two sets of power circuits which operatein different phases. The first power circuit includes a PMOS switchingtransistor 172, an NMOS switching transistor 173, and an inductor 174.The second power circuit includes a PMOS switching transistor 176, anNMOS switching transistor 177, and an inductor 178. The inductor 174 andthe inductor 178 are connected to a common capacitor 179 and the outputsfrom the first and second power circuits are added.

A semiconductor chip 1 includes power domains 130 to 132. The powerdomains 130 to 132 include sensors 164 to 166 which output predeterminedinformation indicating, for example, the operation state of each powerdomain to a DCDC control unit 168, respectively. An AD converter 167converts information about a power supply voltage VDD into a digitalvalue and the digital value is supplied to the DCDC control unit 168.The DCDC control unit 168 outputs two PWM signals PWM1 and PWM2 on thebasis of the predetermined information and the output from the DCDCcontrol unit 168 is supplied to a serializer 169. A serial signal fromthe serializer 169 is supplied to a deserializer 170 through anelectrode pad 3 and is then converted into parallel signals. Theparallel signals are supplied to drivers 171 and 175 of the powercircuits.

The DCDC control unit 168 formed in the semiconductor chip 1 rapidlycontrols two PWM signals PWM1 and PWM2 to desired output voltages on thebasis of the predetermined information which is directly supplied fromthe sensors 164 to 166 and outputs the two PWM signals PWM1 and PWM2.The two PWM signals PWM1 and PWM2 are supplied to the serializer 169 andare then converted into a serial signal. Then, the serial signal isoutput from the electrode pad 3. The deserializer 170 converts theserial signal into the parallel signals and the parallel signals aresupplied to the drivers 171 and 175 of the power circuits. The duty ofthe turning on and off of the switching transistors 172 and 173 of thefirst power circuit and the switching transistors 176 and 177 of thesecond power circuit is controlled and the output voltages from thefirst and second power circuits are added. Then, the added voltage issupplied to the electrode pad 2 of the semiconductor chip 1. Since theoutputs from the first and second power circuits are added, it ispossible to increase an output current. In addition, control isperformed such that the time the PMOS switching transistor 172 of thefirst power circuit is turned on deviates from the time the PMOStransistor 176 of the second power circuit is turned on and the outputvoltage from the second power circuit is the maximum at the time theoutput voltage from the first power circuit is the minimum. In this way,it is possible to obtain a power supply voltage VDD whose ripple issuppressed. In addition, the number of power circuits may be furtherincreased by the same structure as described above to increase theoutput current, thereby further reducing the ripple of the power supplyvoltage.

According to this embodiment, the DCDC control unit 168 formed in thesemiconductor chip 1 can rapidly control the power supply voltage VDDsuch that it corresponds to a large current and the ripple thereof isreduced, on the basis of the operation state of each of the powerdomains 130 to 132 which are integrated into the semiconductor chip 1,and supply the power supply voltage VDD to the power domains 130 to 132of the semiconductor chip 1.

FIG. 14 is a diagram illustrating the structure of a semiconductordevice according to a twelfth embodiment. The same components as thosein the first to eleventh embodiments are denoted by the same referencenumerals and the description thereof will not be repeated. Thisembodiment relates to a so-called multi-channel structure in whichdifferent power supply voltages are supplied to power domains formed ina semiconductor chip 1. In this embodiment, the semiconductor chip 1includes four power domains 180 to 183. A voltage of 1.0 V is suppliedas a power supply voltage VDD1 to the power domain 180 through anelectrode pad 222. A voltage of 3.3 V is supplied as a power supplyvoltage VDD2 to the power domain 181 through an electrode pad 223. Avoltage of 1.5 V is supplied as a power supply voltage VDD3 to the powerdomain 182 through an electrode pad 224. A voltage of 2.0 V is suppliedas a power supply voltage VDD4 to the power domain 183 through anelectrode pad 225.

The power domains 180 to 183 include sensors 190 to 193, respectively.The outputs from the sensors 190 to 193 are supplied to DCDC controlunits 194 to 197 provided in the power domains 180 to 183, respectively.An AD converter 230 converts information about the power supply voltageVDD1 into a digital value and the digital value is supplied to the DCDCcontrol unit 194 of the power domain 180. An AD converter 231 convertsinformation about the power supply voltage VDD2 into a digital value andthe digital value is supplied to the DCDC control unit 195 of the powerdomain 181. An AD converter 232 converts information about the powersupply voltage VDD3 into a digital value and the digital value issupplied to the DCDC control unit 196 of the power domain 182. An ADconverter 233 converts information about the power supply voltage VDD4into a digital value and the digital value is supplied to the DCDCcontrol unit 197 of the power domain 183.

Each of the DCDC control units 194 to 197 performs control in theabove-mentioned various control modes. Outputs Set1 to Set4 and Reset1to Reset4 from the DCDC control units 194 to 197 are supplied to aserializer 198 and are then converted into a serial signal. The setsignals Set1 to Set4 correspond to the set signals in theabove-described embodiments. For example, the set signals Set1 to Set4correspond to the set signal which is supplied from the frequency/phaseadjustment circuit 34 to the RS latch circuit 33 in the embodimentillustrated in FIG. 3. The reset signals Reset1 to Reset4 correspond tothe reset signal Resetsignal which are supplied from the digital delayconversion circuit 32 to the RS latch circuit 33 in the exampleillustrated in FIG. 3. The outputs Set and Reset from the serializer 198are supplied to a deserializer 199 through two electrode pads 220 and221. The serializer 199 forms four PWM signals PWM1 to PWM4 and suppliesthe PWM signals PWM1 to PWM4 to drivers 200 to 203. An example of theserializer 198 and the deserializer 199 will be described below.

The first driver 200 controls an output voltage Vout1 from a first powercircuit including a PMOS switching transistor 204, an NMOS switchingtransistor 208, an inductor 212, and a capacitor 216. The second driver201 controls an output voltage Vout2 from a second power circuitincluding a PMOS switching transistor 205, an NMOS switching transistor209, an inductor 213, and a capacitor 217. The third driver 202 controlsan output voltage Vout3 from a third power circuit including a PMOSswitching transistor 206, an NMOS switching transistor 210, an inductor214, and a capacitor 218. The fourth driver 203 controls an outputvoltage Vout4 from a fourth power circuit including a PMOS switchingtransistor 207, an NMOS switching transistor 211, an inductor 215, and acapacitor 219. The power supply voltages VDD1 to VDD4 controlled by theDCDC control units 194 to 197 of the power domains 180 to 183 aresupplied to the four power domains 180 to 183 through electrode pads 222to 225, respectively.

According to this embodiment, the power supply voltages VDD1 to VDD4 ofthe semiconductor device with a multi-channel structure can becontrolled in various control modes and then supplied to the powerdomains 180 to 183, respectively. The DCDC control units 194 to 197formed in the semiconductor chip 1 in which the power domains 180 to 183are formed can rapidly control the power supply voltages VDD1 to VDD4corresponding to the characteristics or operation state of the powerdomains 180 to 183 and supply the power supply voltages VDD1 to VDD4 tothe power domains 180 to 183, respectively. The use of the serializer198 and the deserializer 199 makes it possible to supply signalsrequired to form the PWM signals PWM1 to PWM4 for controlling thedrivers 200 to 203 of the four power circuits to the power circuitsthrough the two electrode pads 220 and 221. Therefore, it is possible toprevent an increase in the number of electrode pads.

FIGS. 15A and 15B are diagrams illustrating examples of the serializer198 and the deserializer 199 which can be used in the embodimentillustrated in FIG. 14. FIG. 15A illustrates an example of theserializer 198. The serializer 198 includes two OR circuits 230 and 231.The set signals Set1 to Set4 are supplied to the OR circuit 230. The setsignal Set and the reset signal Reset, which are the outputs from theserializer 198, are supplied to the deserializer 199 through the pads220 and 221 of the semiconductor chip.

FIG. 15B illustrates an example of the deserializer 199. Thedeserializer 199 includes two counter circuits 232 and 233. The countercircuit 232 counts the set signal Set supplied from the serializer 198and supplies the count result to comparison circuits 240 to 243. Thecounter circuit 233 counts the reset signal Reset supplied from theserializer 198 and supplies the count result to comparison circuits 250to 253. The comparison circuits 240 to 243 each have unique digitalvalues 00 to 11. When the count result from the counter circuit 232 isequal to the digital values, each comparison circuit outputs a pulsesignal (not illustrated) to the set input terminals S of thecorresponding RS latch circuits 260 to 263. Similarly, the comparisoncircuits 250 to 253 each have unique digital values 00 to 11. When thecount result from the counter circuit 233 is equal to the digitalvalues, each comparison circuit outputs a pulse signal (not illustrated)to the reset input terminals R of the corresponding RS latch circuits260 to 263. The RS latch circuits 260 to 263 output four PWM signalsPWM1 to PWM4 whose rising and falling have been controlled by the setsignal and the reset signal. The PWM signals PWM1 to PWM4 are suppliedto the drivers 200 to 203 of the corresponding power circuits,respectively.

FIGS. 16A to 16N are diagrams illustrating the relationship between thesignals supplied to the serializer 198 and the deserializer 199 and thesignals output therefrom. FIGS. 16A to 16D illustrate the set signalsSet1 to Set4 supplied to the serializer 198. FIGS. 16E to 16H illustratethe reset signals Reset1 to Reset4 supplied to the serializer 198. FIG.161 illustrates an output signal Setsignal from the OR circuit 230 ofthe serializer 198. The sets signal Set1 to Set4 supplied to the ORcircuit 230 of the serializer 198 are converted into a serial signalSet. FIG. 16J illustrates an output signal Resetsignal from the ORcircuit 231 of the serializer 198. The reset signals Reset1 to Reset4supplied to the OR circuit 231 of the serializer 198 are converted intoa serial signal Reset. FIGS. 16K to 16N illustrate the PWM signals PWM1to PWM4 which are the output signals from the deserializer 199. Therising and falling of the PWM signals PWM1 to PWM4, which are the outputsignals from the deserializer 199, are controlled by the correspondingset signals Set1 to Set4 and the corresponding reset signals Reset1 toReset4. The RS latch circuits 260 to 263 respond to the set signals Set1to Set4 and the reset signals Reset1 to Reset4 corresponding to thecomparison circuits 240 to 243 and the comparison circuits 250 to 253 inthe deserializer 199 and output the PWM signals PWM1 to PWM4 as theparallel signals. The PWM signals PWM1 to PWM4 are supplied to thedrivers 200 to 203 of the power circuits, respectively.

The set signals Set1 to Set4 and the reset signals Reset1 to Reset4 arethe control signals which are supplied from the control circuit units194 to 197 provided in the power domains 180 to 183 in the embodimentillustrated in FIG. 14. Therefore, the power supply voltages VDD1 toVDD4 can be controlled on the basis of the state of each of the powerdomains 180 to 183. In addition, even when the number of power domainsprovided in the semiconductor chip 1 increases, it is possible toincrease the number of comparison circuits and RS latch circuits in thedeserializer 199 so as to correspond to the number of power domainsformed in the semiconductor chip 1, thereby responding to the increasein the number of power domains. In this case, two signals, that is, theset signal Set and the reset signal Reset can be output from theserializer 198. Therefore, two power supply pads may be provided in thesemiconductor chip in order to supply signals from the serializer 198 tothe deserializer 199. In the multi-phase structure according to theembodiment illustrated in FIG. 13, even when the number of powercircuits increases, it is possible to use the same serializer 198 anddeserializer 199 as those in the structure illustrated in FIG. 15.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A semiconductor device comprising: a firstsemiconductor chip which includes a first power supply terminal and intowhich a circuit block operated by a power supply voltage supplied to thefirst power supply terminal is integrated; a power circuit that includesa switching transistor and supplies the power supply voltage to thefirst power supply terminal; and a control circuit that is formed on thefirst semiconductor chip and generates a control signal for controllingthe turning on and off of the switching transistor in response to aninformation signal from the circuit block and a voltage informationsignal corresponding to the power supply voltage.
 2. The semiconductordevice according to claim 1, wherein the power circuit includes a firstswitching transistor and a second switching transistor, and the controlsignal generated by the control circuit is used to control the ratio ofthe turning on and off of the first and second switching transistors. 3.The semiconductor device according to claim 2, wherein the informationsignal includes a signal indicating the operating frequency and phase ofthe circuit block, and the control circuit generates a signal forcontrolling the switching transistors of the power circuit such that theswitching transistors are turned on and off at a frequency and/or aphase different from the operating frequency and/or phase of the circuitblock.
 4. The semiconductor device according to claim 3, wherein thecontrol circuit includes: a voltage error signal generation circuit thatcompares the power supply voltage with a predetermined reference voltageand generates a first control signal on the basis of the comparisonresult; a frequency error signal generation circuit that compares theoperating frequency and phase of the circuit block with the frequencyand phase of the power circuit and generates a second control signal onthe basis of the comparison result; and a circuit that generates asignal for controlling the ratio of the turning on and off of theswitching transistors of the power circuit in response to the firstcontrol signal and the second control signal.
 5. The semiconductordevice according to claim 1, wherein the information signal includes asignal indicating the operating frequency and phase of the circuitblock, and the control circuit generates a signal for controlling theswitching transistors of the power circuit such that the switchingtransistors are turned on and off at a frequency and/or a phasedifferent from the operating frequency and/or phase of the circuitblock.
 6. The semiconductor device according to claim 5, wherein thecontrol circuit includes: a voltage error signal generation circuit thatcompares the power supply voltage with a predetermined reference voltageand generates a first control signal on the basis of the comparisonresult; a frequency error signal generation circuit that compares theoperating frequency and phase of the circuit block with the frequencyand phase of the power circuit and generates a second control signal onthe basis of the comparison result; and a circuit that generates asignal for controlling the ratio of the turning on and off of theswitching transistors of the power circuit in response to the firstcontrol signal and the second control signal.
 7. The semiconductordevice according to claim 1, wherein the control circuit includes: avoltage error signal generation circuit that compares the power supplyvoltage with a predetermined reference voltage and generates a firstcontrol signal on the basis of the comparison result; a frequency errorsignal generation circuit that compares the operating frequency andphase of the circuit block with the frequency and phase of the powercircuit and generates a second control signal on the basis of thecomparison result; and a circuit that generates a signal for controllingthe ratio of the turning on and off of the switching transistors of thepower circuit in response to the first control signal and the secondcontrol signal.
 8. The semiconductor device according to claim 1,wherein the information signal includes a signal indicating an operatingcurrent of the circuit block, and the control circuit generates a signalfor controlling the operating current so as to increase at apredetermined slope.
 9. The semiconductor device according to claim 8,wherein the control circuit includes: a current control circuit thatcompares a reference current which increases at a predetermined slopewith the operating current of the circuit block and generates a thirdcontrol signal on the basis of the comparison result; and a circuit thatgenerates a signal for controlling the ratio of the turning on and offof the first and second switching transistors in response to the thirdcontrol signal.
 10. The semiconductor device according to claim 1,wherein the information signal includes a mode change signal forchanging an operation mode of the circuit block, and the control circuitgenerates a signal for controlling the ratio of the turning on and offof the switching transistors of the power circuit on the basis of themode change signal.
 11. The semiconductor device according to claim 1,wherein the information signal includes an on/off event informationsignal for the operation of the circuit block, and the control circuitgenerates a signal for controlling the ratio of the turning on and offof the switching transistors of the power circuit on the basis of theon/off event information signal.
 12. The semiconductor device accordingto claim 1, wherein the information signal includes a signal indicatingtemperature information of the circuit block, and the control circuitgenerates a signal for controlling the ratio of the turning on and offof the switching transistors of the power circuit on the basis of theinformation signal indicating the temperature information.
 13. Thesemiconductor device according to claim 12, wherein the control circuitincludes: a first error calculation circuit that compares apredetermined reference voltage with the power supply voltage andcalculates a first error signal; a second error calculation circuit thatcompares a predetermined reference temperature signal with thetemperature information of the circuit block and calculates a seconderror signal; a third error calculation circuit that compares apredetermined reference delay signal with information about a delay inthe operation of the circuit block and calculates a third error signal;and an adder circuit that adds outputs from the first to third errorcalculation circuits.
 14. The semiconductor device according to claim 1,wherein a plurality of power domains is formed in the firstsemiconductor chip, the information signal includes a signal indicatingan operating voltage of each of the plurality of power domains, and thecontrol circuit generates a control signal for increasing the powersupply voltage on the basis of predetermined threshold voltageinformation and the signal indicating the operating voltage.
 15. Thesemiconductor device according to claim 1, wherein a plurality of powerdomains is formed in the first semiconductor chip, the informationsignal includes a signal indicating an operating voltage of each of theplurality of power domains, and the control circuit generates a controlsignal for reducing the power supply voltage on the basis ofpredetermined threshold voltage information and the signal indicatingthe operating voltage.
 16. The semiconductor device according to claim1, wherein the power circuit includes a first power circuit that outputsa first output voltage and a second power circuit that outputs a secondoutput voltage, and the control circuit generates a control signal forcontrolling the turning on and off of each of the first power circuitand the second power circuit.
 17. The semiconductor device according toclaim 16, further comprising: a serializer that is formed in thesemiconductor chip and converts the control signal of the controlcircuit into a serial signal; and a deserializer that is providedoutside the semiconductor chip, receives an output signal from theserializer, and converts the output signal from the serializer intoparallel signals.
 18. The semiconductor device according to claim 1,wherein the power circuit includes a first power circuit that outputs afirst output voltage in a first phase and a second power circuit thatoutputs a second output voltage in a second phase different from thefirst phase, the control circuit outputs control signals for controllingthe first power circuit and the second power circuit, and a voltageobtained by adding an output voltage from the first power circuit and anoutput voltage from the second power circuit is supplied to the firstpower supply terminal.
 19. The semiconductor device according to claim18, further comprising: a serializer that is formed in the semiconductorchip and converts the control signal of the control circuit into aserial signal; and a deserializer that is provided outside thesemiconductor chip, receives an output signal from the serializer, andconverts the output signal from the serializer into parallel signals.20. The semiconductor device according to claim 19, wherein theserializer includes an OR circuit to which a signal for controlling therising of the control signal or a signal for controlling the falling ofthe control signal is supplied for controlling the turning on and off ofthe switching transistor, and the deserializer includes a countercircuit that responds to the output signal from the serializer, acomparison circuit that outputs a signal when a count value of thecounter circuit is equal to a predetermined value, and an RS latchcircuit that outputs a control signal whose rising and falling arecontrolled, in response to the output signal from the comparisoncircuit.